Testing Smart Contracts

Testing Smart Contracts

Smart contracts are immutable once deployed. Bugs can lead to permanent loss of funds. Rigorous testing before deployment is not optional — it is essential.

Testing Pyramid

          ┌──────────────┐
          │   Manual /    │
          │   Audit       │  ← Fewest, most expensive
          ├──────────────┤
          │  Integration  │
          │   Tests       │  ← Multiple contracts interacting
          ├──────────────┤
          │    Unit       │
          │    Tests      │  ← Most tests, cheapest
          └──────────────┘

  Unit Tests: Test individual functions in isolation
  Integration Tests: Test contract interactions
  Audits: Professional security review

Unit Testing with Hardhat

  const { expect } = require("chai");
  const { ethers } = require("hardhat");

  describe("Token", function () {
    let token, owner, addr1;

    beforeEach(async function () {
      [owner, addr1] = await ethers.getSigners();
      const Token = await ethers.getContractFactory("Token");
      token = await Token.deploy("MyToken", "MTK", 1000000);
    });

    it("Should set correct name and symbol", async function () {
      expect(await token.name()).to.equal("MyToken");
      expect(await token.symbol()).to.equal("MTK");
    });

    it("Should assign total supply to deployer", async function () {
      expect(await token.balanceOf(owner.address))
        .to.equal(1000000);
    });

    it("Should transfer tokens between accounts", async function () {
      await token.transfer(addr1.address, 100);
      expect(await token.balanceOf(addr1.address))
        .to.equal(100);
    });

    it("Should fail if sender lacks balance", async function () {
      await expect(
        token.connect(addr1).transfer(owner.address, 1)
      ).to.be.revertedWith("Insufficient balance");
    });
  });

Integration Testing

  describe("DeFi Integration", function () {
    it("Should deposit, borrow, and repay", async function () {
      // Deploy both LendingPool and Token contracts
      // Deposit collateral
      // Borrow against collateral
      // Verify balances
      // Repay loan
      // Verify full cycle
    });
  });

Security Audit Checklist

  ✓ Reentrancy vulnerabilities
  ✓ Integer overflow/underflow
  ✓ Access control (onlyOwner, roles)
  ✓ Front-running risks
  ✓ Flash loan attack vectors
  ✓ Oracle manipulation
  ✓ Denial of service (DoS)
  ✓ Unchecked external calls
  ✓ Centralization risks
  ✓ Gas limit and DoS with block gas